This invention pertains to apparatus for measuring a load applied to a cantilever-type beam. In particular, it relates to such apparatus in which this kind of measurment may be made extremely accurately, and without regard to the exact point along such a beam where a load is applied.
There are various applications in which cantilevertype beams are subjected to loads whose levels are desired to be monitored. Such beams often form part of, or are operatively associated with, other equipment wherein the level of loading is desired to be followed. An example would be the handle of a torque wrench. In the past, strain gauges and like devices, or other kinds of load-measuring means, have been suitably secured to such beams for the purpose of deriving the desired load information. However, a consideration which has substantially always been of concern heretofore, is knowledge with respect to the exact point along a beam where a load is applied. In other words, final calculation, or indication, of the desired load information has depended upon accurate knowledge of the point of load application.
A general object of the present invention is to provide load information of the type outlined, which is capable accurately of performing this function, without the requirement for there being any knowledge regarding the exact point along a beam where a load is applied.
Another object of the invention is to provide such apparatus which can be incorporated extremely simply in a wide variety of cantilever-type beam devices.
Still another object is to provide such apparatus which is extremely simple in construction, and economical to manufacture.
The present invention is based on the concept that if a pair of devices, such as elongated stiff fingers, are mounted at a pair of points spaced along a cantilever-type beam, with dispositions tangent to lines parallel to the beam's neutral axis adjacent the points where the devices are attached, then, when the beam bends under substantially right-angle loading, overlapping extensions of these devices will separate, or tend to separate, in a manner directly relatable to the amount of the load producing such bending. The only restriction as to where a load must be applied for this relationship to hold true, is that the load must be applied no further inwardly along the beam than the point of attachment of the outermost device.
In one embodiment of the invention the proposed devices comprise elongated, straight, stiff fingers attached as described above -- the separation between which, at a selected place between their mountings is measured in a visual manner. In another embodiment, the devices comprise portions of a unitary elongated deflection sensor having a central "flexure" -- a region weakened to have a relatively low longitudinal spring rate as compared with the other portions of the unit. The center of this flexure is functionally relatable to that place just mentioned where separation would be measured if the tangent devices were nonumitary. In the case of this second modification, bending occurs in one or both of the portions of the unit extending away from the flexure, which bending is directly relatable to the load that produces it. A third modification discussed comprises nonunitary devices that contact each other.
The reasons why apparatus such as that just generally outlined will function to provide accurate loading information on a cantilever beam, independently of the point of load application, will be developed more fully below. It will also become apparent how the proposed apparatus is relatively simple in construction, and may readily be incorporated in a wide variety of appications.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.